Sound attenuating chamber

ABSTRACT

A short overall length quarter wave or Quincke tuner for use in automotive exhaust systems to attenuate predetermined sound frequencies is provided by a folded or box structure or a helical structure providing a zig-zag sound path with an effective acoustical length that is materially greater than the physical length of the tuner.

O Unlted States Patent [151 3,655,011 Willett [451 Apr. 11, 197 2 [54] SOUND ATTENUATING CHAMBER 3,396,812 8/1968 Wilcox et a1... "181/48 [72] Inventor: Earl G. wine, Racine Wis 3,429,397 2/1969 Case ..18l/72 [73] Assignee Tenneco lnc., Racine, Wis. FOREIGN PATENTS OR APPLICATIONS J Gfat Britain [2]] Appl. No.: 45,041 Primary Examiner-Richard B. Wilkinson Assistant Examiner-John F. Gonzales 52 US. Cl 181/48, 181/59 Am'"ey fiamess Dmkey [5 1] Int. Cl ..F01n 1/02 57 ABSTRACT [58] Field ofSearch ..l81/48, 54, 59, 53,362, 72 1 A short overall length quarter wave or Qumcke tuner for use 56] References Cited in automotive exhaust systems to attenuate predetermined sound frequencies is provided by a folded or box structure or a UNITED STATES PATENTS helical structure providing a zig-zag sound path with an effect' t' 11 ththt' t I! 1 th th h 3,402,7ss 9/1968 Powers et al 1 8 1/72 x l ffig 'ffif ai a ma em y gm er e p 3,525,419 8/1970 Cassei ..181/48 3,194,341 7/1965 Haag ..181/54 X 2 Claims, 6 Drawing Figures SOUND ATTENUATING CHAMBER It is the purpose of the invention to make the quarter wave or Quincke principle of sound attenuation of more practical use in the design of exhaust systems for internal combustion engines used in motor vehicles.

The invention accomplishes this by means of a quarter wave length tuner that is shaped to provide a zig-zag path for sound waves. Use of this type of path reduces the overall length of the tuner while still permitting a relatively long acoustic length. The device is therefore more suitable for use in the restricted and oddly shaped spaces available for exhaust system components on the chassis of modern automobiles.

DESCRIPTION OF THE DRAWINGS FIG. I is a schematic side elevation of an internal combustion engine having an exhaust system using one form of quarter wave length tuner construction embodying the invention;

FIG. 2 is a cross section along the line 2-2 of FIG. I on an enlarged scale;

FIG. 3 is a section along the line 3-3 of FIG. 2;

FIG. 4 is a schematic side elevation of an internal combustion engine having an exhaust system utilizing a modified form of quarter wave length tuner embodying the invention;

FIG. 5 is an enlargement of the structure within the circle 5 of FIG. 4; and

FIG. 6 is a cross section along the line 6-6 of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION An internal combustion engine 1 has an exhaust system 3 connected to the exhaust manifold 5 for delivering gases from the manifold to the rear of an automobile and attenuating sound therein enroute. The exhaust system 3 comprises an exhaust pipe 7 which conducts gases from the manifold to a muffler 9 of any suitable construction which in turn is connected to a tailpipe 11 that discharges the silenced gases to atmosphere.

In accordance with this invention, a quarter wave length tuner 13 is connected to the exhaust pipe 7 at an appropriate pressure point or position with respect to the anti-node of the frequency to be attenuated as is known to those in this field. For connection purposes, the tuner 13 has a combination inlet and outlet 15 which is welded or otherwise firmly and sealingly secured around an opening in the wall of the pipe 7 and which may be of various lengths to suit the frequency being attenuated and the mounted positions of the tuner. As shown best in FIGS. 2 and 3, the tuner 13 comprises a substantially rectangular box 17 which is closed on all sides and provides an internal chamber 19. The space 19 within the box 17 is subdivided by a plurality of parallel, spaced, and staggered partitions or baffles which extend most but not all the way across the width of the box 17. Thus, the partitions 21 and 23 extend from one wall 24 toward but stop short of the opposite wall and in the reverse sense the partitions 25 and 27 extend from the second wall 28 toward but short of the first wall. The spacing of the ends of the partitions from the respective walls is preferably substantially equal to the spacing between the partitions.

As seen best in FIG. 3, this staggered arrangement of the baffles provides a zig-zag path of substantially uniform cross sectional area for the travel of sound waves from the inlet member 15 to the surface 29 at the end of the path and reflection back from the surface 29 to effect cancellation. The

length of the zig-zag path along the centerline leading from the connection of the tuner 13 to the tube 7 to the surface 29 comprises the efi'ective acoustic length of the tuner 13 and this, as is well known, is selected to be approximately one quarter of the wave length that it is desired to attenuate and for which the inlet 15 is positioned. In this form of the invention the separate sections of the zig-zag path are substantially paralleltq each other making for a very compact arrangement with minimum overall physical dimensions. The box can therefore be positioned in various unused spaces beneath the vehicle body (not shown) such as a fender wall, beneath a seat, in a trunk, etc. Since relatively long effective lengths are obtainable, the arrangement is especially useful in silencing low frequencies.

In FIG. 4 there is again an internal combustion engine 51 having an exhaust system 53 receiving gases from the exhaust manifold 55 and including an exhaust pipe 57 and a muffler 59 that is connected to the tailpipe 61. Gas flows from the exhaust manifold 55 through the pipe 57 to the muffler 59 and then through the tailpipe 61 to atmosphere.

The exhaust system 3 includes a quarter wave length tuner 63 that is in the form of a unifonn diameter pipe that is helically wrapped around the gas flow tube 57. One end of the pipe 65 is connected to open into the pipe 57 at point 67 and the other end of the pipe is closed as seen at 69. The point 67 is located as close as possible to an optimum pressure point or anti-nodal point for the frequency to be attenuated as is known to workers in this field.

The corkscrew shape of the tube 65 provides it with oppositely extending turns 71 and 73 which provide a zig-zag path of a helical naturethrough which-sound can travel from the inlet 67 to the end 69 of the tuner, the effective internal length of the tuner tube 65 being approximately one quarter of the wave length of the frequency to be attenuated.

In the arrangement of FIG. 4 tuner pipe 65 is in contact with the exhaust pipe 57 and therefore is in heat transfer relationship with it. The heat of the exhaust gases passing through pipe 57 will therefore be transmitted to the pipe 57 and pipe 65 to the interior of the tuner. While this has some adverse effect on the efficiency of tuning it has the advantage of broad-banding the tuner 63 so that a wider spectrum of frequencies may be attenuated.

Modifications in the specific structures may be made without departing from the spirit and scope of the invention.

1 claim:

1. In an exhaust system for an internal combustion engine, said engine producing various sound frequencies including at least one low frequency to be silenced by the exhaust system, said exhaust system including a gas flow tube, and a quarter wave length tuner connected to said gas flow tube in parallel with it and having a combination inlet and outlet opening and closed tube means extending from said opening, the internal length of the tube means being substantially one quarter of the wave length of said low frequency, said tube means being substantially helical in shape and coiled around the gas flow tube and in heat transfer relationship with it.

2. In an exhaust system for an internal combustion engine, said engine producing various sound frequencies including at least one low frequency to be silenced by the exhaust system, said exhaust system including a gas flow tube, and a quarter wave length tuner connected to said gas flow tube in parallel with it and having a combination inlet and outlet opening and comprising a closed box having staggered parallel baffles therein providing a zig-zag path having a length equal to substantially one quarter of the wave length of said low frequency. 

1. In an exhaust system for an internal combustion engine, said engine producing various sound frequencies including at least one low frequency to be silenced by the exhaust system, said exhaust system including a gas flow tube, and a quarter wave length tuner connected to said gas flow tube in parallel with it and having a combination inlet and outlet opening and closed tube means extending from said opening, the internal length of the tube means being substantially one quarter of the wave length of said low frequency, said tube means being substantially helical in shape and coiled around the gas flow tube and in heat transfer relationship with it.
 2. In an exhaust system for an internal combustion engine, said engine producing various sound frequencies including at least one low frequency to be silenced by the exhaust system, said exhaust system including a gas flow tube, and a quarter wave length tuner connected to said gas flow tube in parallel with it and having a combination inlet and outlet opening and comprising a closed box having staggered parallel baffles therein providing a zig-zag path having a length equal to substantially one quarter of the wave length of said low frequency. 